Paper Sizes & Weights Explained

Even though paper is one of the most familiar materials in the modern world, when it comes to artist’s papers, sizes, proportions, and weights can seem mysterious. Differences between writing, printing, and artist’s papers further add to the complexity, and standards set hundreds of years ago still influence modern measurements. In order to understand the reason behind paper sizes and weights, we need to look at the history of paper before industrialization, and how it was made and used over the centuries.

The history of paper reaches back two thousand years. While ancient precursors like papyrus reed mats from Egypt and animal-derived parchment and vellum served a similar purpose, they were limited in scale and availability, and were often reserved for significant ceremonial and administrative purposes.

Image (right): Left - Greek letter written on papyrus, early 3rd century, Right - Illuminated manuscript, ink, tempera and gold on vellum, 1460s

Paper had existed in China for about two hundred years before being perfected in AD 105, by Cai Lun, a Han Dynasty court official. Cai Lun’s process used rag trimmings, tree bark, old fishing nets, and other waste for pulp. Later the lining of mulberry bark became the preferred raw material, an abundant resource in ancient China as a by-product of silk cultivation.

Image (left): Papermaking as described by Cai Lun

The invention of papermaking provided a way to create a large, continuous supply of sheets in regular surfaces and sizes that could be made from by-products of existing industry. This allowed wider use of paper for practical purposes like packaging and wrapping, as well as for drawing and writing.

Image (right): Papermaking in Tawang, Arunachal Pradesh

Papermaking spread through Asia over the next several centuries, but papyrus, adopted from Egypt by Greece and widely distributed in the Roman Empire, remained in use elsewhere until the late 8th century, when the first papermill in Persia was established. It was during this period that the word “ream” for a standard stack of paper originated, derived from the Arabic word for bundle.

The first known paper mill in Europe dates to 1056 in Spain, and shortly after, one was established in Sicily. By the 12th century, the first paper mill was established at Fabriano, Italy, where some of the finest papers are still made today. Western paper was largely made of pulp from textile rags, a preference that was reinforced by the Black Death, with a huge abundance of old cloth left by plague victims. (We still refer to paper made from cotton and linen as “rag paper”.) As a result of this windfall of raw material, European papermaking advanced and expanded, and would be ready to supply the emerging printing industry launched less than a century later by the invention of movable type printing.

As papermaking spread across Europe, each country established its own standards for sizes and weights. Sheet sizes and proportions were influenced by a lot of variables, like the purpose of the paper, and local equipment and production techniques. For hundreds of years, paper was made on a hand-held screen and frame called a “mold and deckle”, and to make things more complex, sometimes paper was measured by the inside of the mold and deckle, and sometimes by the outside. Efficiency in folding and cutting full sheets was an important consideration, and the practical limitations of equipment also influenced the standard properties of paper. Traditional sheet proportions are so ingrained in our concept of visual harmony, that they’ve had a durable influence on the sizes art papers come in today.

Image (right): Row of hammer mills for processing pulp, Italy

In 1836, Imperial sizes were established in Britain, including existing names like “double elephant”, “foolscap”, and “atlas”. Originally, some of these names would have referred to a recognizable watermark or insignia, or a specific purpose, like “cartridge paper” which derived from an Italian word for a paper pouch for holding gunpowder. Germany and France had similar, parallel systems defined separately.

Image (left): Fibonacci spiral, illustrating the Golden Ratio

Traditional standards for measuring weight of paper were also closely related to sheet size. Almost every artist is familiar with a system of measuring paper weight in pounds, which is also called “basis weight”. Through experience, artists come to know what to expect from “one hundred forty pound” or “three hundred pound” paper, but at first, these designations can seem illogical. How, for instance, can a “two hundred sixty pound” sheet seem so much lighter than a thick, heavy three hundred pound sheet? The key is that “basis weight” is determined by the weight of a ream of full-size sheets of paper. A ream made up of bigger sheets will have a larger basis weight, even if the sheets are made of comparatively lighter weight material. Interestingly, while a ream of paper today is five hundred sheets, it used to be four hundred eighty sheets, or twenty “quires” of twenty-four. (The word “quire” derives from a Latin word for a set of four.)

Only fine, artisanal paper is made on a mold and deckle today. Modern papermaking equipment that can produce continuous rolls, and cylinder machines that automatically produce individual sheets make it possible to make paper in any size and proportion, eliminating the equipment limitations that once influenced paper sizes.

Rational, universal standards for paper sizes were proposed beginning in the late 18th century, which were influenced by mathematics and by philosophical concepts about intrinsic harmony, like the golden ratio. Notably, physicist Georg Christoph Lichtenberg advocated for using the relationship of the square root of two to one. This was the early origin of European standard paper sizes later adopted, and still in use today.

Under modern systems, paper weight is now given in grams per square meter, which is always the same regardless of sheet size. Where in the past, local craft guilds set sheet standards, today paper sizes are set by organizations that set all sorts of materials standards– the American National Standards Institute, or ANSI in North America, and International Organization for Standardization, or ISO in Europe and elsewhere. Traditional sizes and weights still survive, however, in art papers, which are used in painting and printmaking.

Image (left): Traditional papermaking workshop and equipment

Paper is all around us, and yet to artists, it never seems commonplace. We use paper for the most mundane and functional purposes, but also for our most sacred and significant documents and works of art. Maybe that’s why we’ve retained so much of what’s historical and traditional in how we make, measure, and weigh the products of this foundational human technology.